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Old 06-28-2010, 05:06 PM   #1
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Default MS2 ignition input mods

Forgive me if this is a dumb question but Im upgrading to MS2 and trying to work out all the ignition stuff.

Currently, Im using the 3.57 board with the "normal" ignition mods per diyautotune's writeup along with the stock '99 cam/crank sensors and a modded crank wheel. I've had this setup for ~2 years now and it runs mint...never had so much as a hiccup from it.

So to the point; is there something Im missing here that requires changing the circuit for MS2, or can I leave it as-is?
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Old 06-28-2010, 05:29 PM   #2
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Well, for starters, the "standard" input circuits are in fact pretty hokey. One (CKP) has the sensor sinking enough current to power an optoisolator at 12 volts, the other (CMP) ties the sensor directly to a CPU pin with no isolation at all. From a EE standpoint, it's a non-optimal design which represents a compromise between robustness and ease of construction / minimal parts count.

Some folks have posited that the NB's sensors are somehow noisier / weaker / less resilient to noise / (something else) than the NA's CAS, and therefore developed a more respectable circuit for it. Abe's, in particular, was build by reverse-engineering the input circuits on a stock '00 ECU.

Realistically speaking, some cars / sensors / Megasquirts seem less likely to experience trigger-related problems than others. You are apparently one of the lucky ones. Others of us have had trouble making the "standard' circuits work reliably even on an NA CAS.

In my opinion, either Abe / Jason-style comparator circuit or the newer MAX9924/9926-based circuit should be used on all cars with logic-level crank/cam sensors.
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Old 06-29-2010, 06:16 PM   #3
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Thanks for the reply, Joe.

I wonder what it is that made mine work out...I used it before in parallel with the stock ecu and using an NA CAS and it worked great with that too. Maybe something with the 3.57 board? Karma evening out all the crap that was a huge hassle? lol
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